To screen, or not to screen?

For men with cancerous prostate glands, ignorance may sometimes be bliss

GEORGE FOREMAN, a former heavyweight boxing champion of the world, clenches his fists, flexes his pecs—and advises his fellow Americans to let a doctor finger their prostate glands once a year. Under his picture, which graces the American Cancer Society's latest poster promoting digital rectal examinations, is the motto: “Real Men Get It Checked.”

A beefy boxer with nine children is the perfect icon for a campaign to convince men that being tested for prostate cancer will not compromise their masculinity. Being black, Mr Foreman may also appeal to a group perhaps two-thirds more likely than whites to succumb to the disease. All in all, a splendid advertisement for a worthy cause. Or is it?

Doctors are no longer confident that widespread screening for prostate cancer does more good than harm. In an echo of recommendations by various bodies that women under the age of 50 should not undergo mammograms to check for breast cancer, the American College of Physicians has just come out against routine tests for prostate cancer. (Ironically, the American Cancer Society has just gone back to the idea of routine mammograms for women in their 40s, and the country's National Cancer Institute is expected to do the same.) Last year, the National Cancer Institute organised a 2,000-patient trial to determine whether surgery prevents more deaths than inaction, but the results will not arrive before 2010. In the meantime, the debate about screening is distorted by the viciousness of the disease—and by the awfulness of current treatment.

The prostate is a gland the size of a walnut that sits under the bladder and helps make seminal fluid. Roughly one man in five living in a rich country will develop a prostate tumour during his life. Most of these tumours will not grow fast enough to cause trouble before he dies of something else, but prostate cancer still kills more American men (about 40,000 a year) than any other cancer bar that of the lungs. Indeed, it claims almost as many lives as breast cancer although, since its victims tend to be older, it accounts for many fewer lost years of life (see chart).

The biggest problem with screening is working out whether a tumour is malignant. Two tests are commonly used to determine risk: a blood test for a compound called prostate-specific antigen (PSA), and a digital rectal probe for suspicious lumps. Positive results are generally followed by a transrectal needle biopsy (which is as uncomfortable as it sounds) to see if a lump is cancerous. Sadly, none of these tests can predict how nasty a growth will turn.

Common sense might suggest that an aggressive screening programme would help to catch cancers early, enabling surgeons to intervene before they spread, and thus preventing lots of premature deaths. William Catalona, chief urologist at the Washington University School of Medicine in St Louis, contends that an estimated 6.3% drop in American prostate-cancer mortality figures between 1991 and 1995, the first reduction in 30 years, is due to PSA tests. He says the tests have reduced from 70% to 30% the proportion of prostate tumours that are not detected until it is too late to treat them. In the time that it will take for the trial data on screening to emerge, he says, half a million Americans will die of prostate cancer.

Along with the American Cancer Society, Dr Catalona favours a campaign to have all men aged between 50 and 70 given annual check-ups. Proponents of prostate screening point to the success of routine mammography for women over 50 in greatly reducing the breast-cancer mortality rate. But others argue that the “common sense” approach is wrong because the two diseases differ in a crucial way.

Masterful inactivity

Since it is generally a disease of older men, and because it develops slowly, most of those who harbour cancerous prostates die with them, not of them. For every fatal tumour detected by screening, five are found that could safely be left alone, according to James Hanley and Maurice McGregor at the Conseil d'Evaluation des Technologies de la Sant

e

in Quebec. But few men, knowing they have a tumour, are content to let it sit there.

Peter Albertsen, a urologist at the University of Connecticut Health Centre in Farmington, argues that mass screening, besides being expensive, will lead to thousands of unnecessary operations. And such interventions are not risk-free. A survey of research sponsored by Britain's National Health Service suggests that radical prostatectomy (cutting it out) causes incontinence in as many as 27% of patients and impotence in as many as 85% of them (though many surgeons claim much better averages). For radiotherapy, the figures are up to 6% for incontinence and 40% for impotence—although newer methods, such as the direct application of radioactive pellets to the tumour, are said to be not as bad.

The fundamental problem is that little is known about the disease. Even the recent fall in prostate-cancer mortality could be due not to screening and treatment but to changes in diet or other causes.

All this suggests that the money which would be spent on a nationwide screening programme in America ($12 billion-28 billion in the first year alone, reckons Dr Albertsen) might be better employed in finding out more about the disease and its causes. Teasing apart the genetic and environmental factors could help people to lead healthier lives—and identify those for whom early screening is advisable.

For example, black men, and men with relations who have developed prostate cancer, seem to be more at risk than most. For others, a change of diet might help. Japanese men living in Japan, where low-fat dishes like tofu and sashimi are popular, rarely get prostate cancer. But those who emigrate to North America suffer more often. Also, prostate tumours grow more slowly in mice dining on low-fat foods than in those gorging on lipids.

Money might also be better spent on the development of gentler treatments. “Keyhole” surgery for prostate cancer is currently in its infancy, but it may turn out to be just as effective as the traditional invasive method. Cryosurgery—whereby a metal probe is inserted into the tumour and the cancerous cells are destroyed by freezing—also looks hopeful, though it sometimes causes dangerous complications such as a bowel/ bladder fistula.

Best of all, though, would be screening methods that made it easier to distinguish between those tumours likely to grow into something lethal, and those likely to remain benign. Luckily, research is nurtured by several rich men who have suffered from the illness. One such, the “junk bond” billionaire Michael Milken, has teamed up with Leroy Hood, a molecular biologist at the University of Washington, in Seattle, in a project that compares thousands of samples of cancerous tissue with normal prostate cells, in the hope of finding biological markers that give warning of danger. For the time being, however, real men will have to decide for themselves.